CNC gear machining contour shape is often a variety of objects, the contour is usually a straight line, arc, spiral, parabola and typical lines to describe the free curve, etc.
In the numerical control device is generally more or less with the linear control method, namely interpolation control algorithm.
One of the most basic is linear and arc interpolation.
In numerical control device with a linear interpolation algorithm, the procedure formulation can greatly simplify the parts processing.
Usually only to provide necessary to describe the linear related parameters, such as the straight line, providing its starting point and end point;
For circular arc, provides a starting point to the end, the circle or reverse circle and circle position relative to the starting point.
Therefore, in order to realize the trajectory control, it is necessary to satisfy real-time calculated lines in the process of movement and feed speed requirements among a number of points (
Between the start and end)
, this is the interpolation in CNC technology (
The concept of.
Accordingly, for interpolation are defined as follows: the so-called interpolation is given feed speed and the requirements of a given contour lines, between the contour of the known point, determine some of the intermediate point method, this method is called interpolation method or interpolation principle.
For each method (
May use different calculation method, the calculation method of the concrete is called interpolation algorithm.
For profile control system, the most important function is the interpolation function, this is because the interpolation arithmetic is in the process of machine tool movement in real time, namely in the limited time, each axis must be real-time allocation of corresponding position control and speed control information.
Profile control system is because of the interpolation function, to work out all kinds of complex shape parts.
To say the interpolation function is the essential characteristics of profile control system.
Therefore, the advantages and disadvantages of interpolation, will directly affect the performance of the CNC system.
Its implementation in the numerical control device there are three main steps, the following circular arc interpolation process of processing, for example.
Below for processing arc trajectory L, starting point for the P0, end point for Pe.
CNC device will use the following three steps of the circular arc interpolation: 1.
Approximation processing CNC device according to the system of the interpolation time delta t and processing required in the feed rate F, will be divided into by a number of short line delta L Ll, delta L2, & hellip;
Here, delta Li, delta t = F (
When delta t = 0, line segment close to the sum of arc L: of course, with linear delta Ll arc exists approximation error & delta;
, but as long as & delta;
Delta Li short enough)
Small enough, always can meet the parts processing requirements.
When F is constant, due to the constant for a certain numerical control system for constant, so the delta Li delta L length are constant, but its slope and the position on the L.
Interpolation operation after calculate the delta Li, must break it down into the x axis and y axis mobile component and (
In the period of time)
, they will be as the delta mound on on the location of the constantly changing, but they meet, and have: Fx = delta Xi/delta ti Fy = delta Yi/delta ti due to delta Li slope is constantly changing, so the feed velocity in the X direction and Y direction component Fx and Fy and the ratio of the Fx/Fy between them are constantly changing.
Delta ti command output will be calculated in time and as the command output to X axis and Y axis, to control their linkage.
Therefore, as long as it can continuously automatic control two feed axis X and Y move in time.
Can realize curve contour parts processing.